This invention relates to a ceramic heater mainly used in a semiconductor industry as a static chuck, wafer prober or the like for drying or sputtering treatment, and more particularly it proposes a ceramic heater changing no resistance value even in a long-time use in an oxidizing atmosphere and having an excellent temperature controllability.
Semiconductor products are generally produced by etching a silicon wafer with a photosensitive resin as an etching resist to form electronic circuits or the like. In such a production method, the liquid photosensitive resin applied onto the surface of the silicon wafer should be dried after the application through a spin-coater. For this end, the drying is carried out by heating the silicon wafer coated with the photosensitive resin by means of a heater.
As such a heater, there has hitherto been used one obtained by forming a heating body on a rear surface of a metallic substrate such as aluminum or the like.
When the heater using such a metallic substrate is used in the drying of the semiconductor product, however, there are the following problems. That is, the substrate of the heater is a metal, so that the thickness of the substrate should be thickened to about 15 mm. Because, when using a thin metal substrate, warping or strain is caused due to thermal expansion resulted from the heating, which affects the wafer placed on such a metallic substrate and heated thereby to cause breakage or tilting. Meanwhile, this problem can be solved by thickening the substrate, but the weight of the heater is increased and becomes bulky.
Further, when the heating temperature of the heater is controlled by changing a voltage or a current quantity applied to the heating element attached to the substrate, if the thickness of the metallic substrate is thick, the temperature of the substrate does not rapidly follow and vary to the change of voltage or current quantity and there is a problem that the temperature control is difficult.
In this connection, there has hitherto been proposed a ceramic heater using a nitride ceramic as a substrate (JP-A-11-40330).
In this conventional technique, however, electron circuit and heating body formed on the substrate are produced by using a sintered metal, so that the scattering in the thickness of the heating body may be caused and hence there are problems that the resistance value is varied so as not to conduct the accurate temperature control and uniform temperature distribution is caused on a heating face of the semiconductor product as a wafer to be heated.
It is an object of the invention to provide a ceramic heater capable of accurately and rapidly conducting the temperature control without scattering of the resistor resulted from the above problems inherent to the conventional ceramic heater, particularly the quality of the heating body.
The inventors have made studies in order to achieve the above object and found that when the heating body to be: formed in the ceramic heater is formed by using a non-sintering metal foil, e.g. a metal foil formed by rolling or plating (particularly electric plating) instead of the above sintered body, the quality (homogeneity) as a heating body is excellent and the problems inherent to the above sintered heating body can be overcome.
And also, it has been found that even when an electrically conductive ceramic is used as the heating body, the above problems inherent to the sintered heating body can be overcome, when a thin film pattern is previously formed, by;embedding the thin film of the electrically conductive ceramic in the substrate or fixing onto the surface of the substrate through adhesion.
Under the above knowledge, the invention is basically a ceramic heater comprising a ceramic substrate and a heating body formed on a surface of the substrate or in an inside thereof and made of a non-sintering type metal foil or an electrically conductive ceramic thin film. Moreover, the non-sintering type metal foil is substantially the same as the non-sintering metal foil.
And also, the invention lies in a ceramic heater comprising a heating body formed on a surface of a ceramic substrate, characterized in that the heating body is made of a non-sintering type metal foil or an electrically conductive ceramic thin film and the metal foil is adhered and fixed to the surface of the substrate with an insulating material layer.
In addition, the invention lies in a ceramic heater comprising a heating body formed on a surface of a ceramic substrate, characterized in that the heating body is made of a non-sintering type metal foil or an electrically conductive ceramic thin film and the metal foil and the substrate are fixed by covering together with an insulating material.
Furthermore, the invention is basically the formation of a heating body made of a non-sintering type metal foil on a surface of a substrate, and is particularly a ceramic heater comprising a heating body formed on a surface of a substrate or in an inside thereof, characterized in that the heating body is made of a non-sintering type metal foil and the metal foil is adhered and fixed onto the surface of the substrate with a heat-resistant resin layer.
Moreover, the invention is a ceramic heater comprising a heating body formed on a surface of a substrate or in an inside thereof, characterized in that the heating body is made of a non-sintering type metal foil and the metal foil and the substrate are covered and fixed together with a heat-resistant resin.
In the ceramic heater according to the invention, it is desirable that a thickness of the non-sintering type metal foils the non-sintering electrically conductive ceramic thin film is 10-50 xcexcm, preferably 10-20 xcexcm.
Moreover, the heating body is desirable to be formed on a face opposite to a heating face.